* When we have world leaders who think might makes right and/or call for violence to "solve issues", there will always be people who rise up and follow their orders/lead. History shows this.
* When we (meaning the people of the world) teach our children (or other children) - by our actions/reactions (or our lack of action/reactions) - that we tolerate (or sanction) violence or revenge with no consequences, they will repeat it and teach the same to their children. The proverb - "Start children off on the way they should go, and even when they are old they will not turn from it." - holds true in the opposite as well.
* So long as there is no justice evil actions will continue. We let murders get off unpunished or give them a "slap on the wrist". Many who do evil are let off (bribery, lying, etc.) simply because they are wealthy or hold positions of power.
